A student is revising Animal Diversity-I: a roundworm thrashes side to side rather than crawling with waves of circular muscles. What should the student write in the answer sheet?

Nematodes mainly have longitudinal muscles and lack circular muscles. Their movement is a whip-like thrashing produced against the elastic cuticle and pseudocoelomic fluid. This MCQ belongs to the Nematoda topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.